This invention relates to the field of electrical machines powered through brushes and sliprings, and more particularly to electrical brush-and-slipring machines provided with chambers running in a ring-shaped pattern circumferentially outward from the sliprings for collecting the dust from the brushes. These collecting chambers are connected to a negative pressure source into which air and brush dust are drawn via the collection chamber suction openings located immediately adjacent to the mounting surfaces of the brushes, and mechanically fastened to brush supports. The brush dust and the air it is contained in are then conveyed to an exterior chamber via a common collecting chamber.
An electrical machine with an apparatus that draws off brush dust and simultaneously cools the sliprings, is known from DE-OS No. 21 23 278. In this known unit, the ring-shaped collection chambers to draw off the brush dust and the cooling air are located on the brush side facing away from the brush supports. They are each connected to radially oriented, pipe-shaped suction channels which extend from the brush to the surface of the slipring, thus forming the suction opening located immediately before the brush mounting surface. The slipring surface is designed with threaded grooves which lead to the suction openings. As the suction openings are restricted to the brush area in the circumferential direction only, the possibility still exists that residual dust remaining in the grooves of the slipring could penetrate to the interspatial area between the suction openings in the slipring area and could be deposited on the machine's insulating parts, thus forming, by a known manner, leakage current paths which reduce the effective dielectric strength. Moreover, in this known machine access to the brushes from both sides for maintenance and equipment checking purposes is impeded. Accordingly, it will be appreciated that it would be highly desireable to provide an electrical machine where the suction openings form unbroken rings, circumferentially located to the slip rings and brushes and, in conjunction with the brushes and sliprings, operate to collect all the brush dust.
It is an object of this invention to improve the brush dust suction arrangement for an electrical machine to reliably draw off all the brush dust. It is a further object of this invention that access to the brushes not be more impeded than the typical normal design without a suction arrangement.